Unit fuel pump-injector



Oct. 31, 1961 w. s. SHADE x-:TAL

UNIT FUEL PUMP-INJECTOR Filed Jan. 3, 1961 fwd United States Patent3,006,556 UNIT FUEL PUMP-INJECTOR i William S. Shade and Conrad A.Teichert, Grand Rapids,

Mich., assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Filed Jan. 3, 1961, Ser. No. 80,063 Claims. (Cl.239-88) This invention relates to fuel injection apparatus, andparticularly -to unit type -fuel pump-injectors for diesel engines.

In such ldevices it is necessary to provide a check valve in theinjection fuel passageway between the pump plunger cylinder and theinjection valve to prevent blow-back of combustion gases from the enginecylinder into the pump cylinder of the injector in the event theinjection valve should happen to stick open during operation. Also,while it has been found -that a needle type injection valve enablesobtaining better timing and accuracy of the quantity of fuel injectionwith resultant increased fuel economy of the engine than do inje-ctionvalves of the poppet type, it is a problem in adapting needle valve typeinjectors for use on certain engines where the opening in the engine forthe injector spray tip or nozzle must be of minimum size.

In accordance with the present invention, `a novel construction of theparts of a unit pump-injector has been devised such that both thediametral extension required for accommodating the check valve 'as wellas the diametral extension of the nozzle or spray tipend aresubstantially reduced, and at the same time the number of parts requiredand their cost of manufacture is also reduced. By relocating the checkvalve so as to seat directly on the lower end face of the pump cylinderbushing and redesigning the injection valve spring retainer, necessityfor either the conventional separate seat for the check valve or for theusual holding tabs on the periphery of the check valve has beenobviated. Also, providing the injection needle valve with an upperpiston portion and a reduced diameter lower or stem portion enablesemploying a relatively long spray tip extension of minimum cross-sectionwithout the necessity of the fuel passage to the tip being extended as adrilled passage through the side Wall of the spray tip for substantiallythe full length of such extension.

A betternnderstanding of these and other objectives and advantages ofthe invention will be had from the following description havingreference to the drawing, wherein:

FIGURE 1 is a longitudinal sectional view through a unit pump-injectorshowing the improved check valve arrangement.

FIGURE 2 is a transverse sectional view taken substantially along line-2-2 of FIGURE 1.

FIGURE 3 is a fragmentary view similar to FIGURE l but showing themodied injection needle valve and fuel passage arrangement in the lowerportion of the injector.

'Referring now in detail to the drawing, and first to FIGURES l and 2,the upper portion of the unit is conventional and comprises a housing 1in which a plunger 2 is reciprocable. Forming an extension of andthreaded to the lower end of the housing 1 is a nut 3 within which fissupported a bushing 4, forming the pump cylinder for the plunger 2. Anannular space 5 surrounding the bushing 4 within the nut is suppliedwith fuel via passages 6 in the housing from an external fuel connection7. The plunger has the usual external metering groove 8 adjacent itslower end by which opening and closing of ports 9 and 10 in the bushingare controlled during each downward stroke of the plunger to deliver apredeter- "ice mined volume of fuel through the lower open end 11 of the'bushing for injection into the engine (not shown) via the spray orices12 at the bottom of the unit. Other details of the upper or pump part ofthe unit are not important to the present invention, and are common toconstructions shown and described in such prior patents as Engel, lr.2,951,643 and Teichert 2,898,051, hence will not require furtherdescription here.

Within the nut 3 :and clamped between the shoulder 13 in its lower endand the lower end of the bushing 4 are a spring retainer 14, a spacerblock 15 and la combined injection valvebody and spray tip 16. The lowerend face 17 of the bushing vserves as a closure seat for a circularcheck Valve disc 13. This disc is disposed in a cavity 19 formed in theupper end of the spring retainer 14, the sides of which cavity extendlaterally beyond the lateral extremities of the open end 11 of the pumpcylinder, and serve to loosely guide the disc 13. A central protuberance20 is formed in the bottom of the cavity 19 and serves to limit openingtravel of the check Valve or disc 18. The cavity 19 also forms the upperend of passage means connecting the open end 11 of the pump cylinderwith the fuel discharge outlets 12, this passage means also including adrilled passage 21 and an annular groove 22 in the retainer 14, adrilled passage 23 through the spacer block 15, a connecting annulargroove 24 and drilled passage 2.5 in the valve body 16 which leads to avalve chamber 26 surrounding the lower end of a needle type injectionvalve 27. At the lower end of this chamber 26 is a fuel discharge outletwhich is controlled by the injection valve 27, this outlet being in theyform of a drilled passage 28 connecting the chamber 26 with the sprayorifices 12. A conical seat 29 for the injection valve is formed 'at thejuncture of this outlet passage with the chamber 26. The upper end ofthe needle Valve is shown provided with a reduced diameter extension 30which engages a spring seat -member 31, and located between this seatmember and the bottom face of the spring retainer 14 is a spring l32which biases the needle valve closed against its seat 29. The spacerblock 15 forms a chamber 33 for the spring and seat and is provided withan opening 38 in its lower end connecting this chamber with acounterbore 34 at the upper end of the bore 35 which is provided in `thevalve body for slidably guiding the needle va'lve 27.

During operation, as fuel pressure is built up in the pump cylinder 4below the plunger 2 it is simultaneously applied via the cavity 19 andconnecting drilled passages and lgrooves to the chamber 26 in the fuelnozzle 16. When this pressure reaches a sui-liciently high valuerequired for injection it raises the needle valve 27 from its seat,permitting discharge of the fuel through the spray orifices 12 in theusual manner. Opening of the needle valve is limited by abutment againstthe spacer block 15 Within the counterbore 34, and in the event theneedle valve should 'for any reason fail to reclose at the end of theinjection cycle, a reverse flow of fuel and combustion gases from theengine via the spray orifices, chamber 26 and connecting passages andgrooves to the cavity 19 and thence into the pump cylinder, is preventedby closing of the check valve -disc 18 against its seat 17 on the pumpcylinder.

The use of such seat 17 for the check vaflve disc not only `eliminatesthe separate seating part conventionally used therefor but requires aless diametral extension of the parts in this area than is required fora conventional disc having its peripheral extremities scalloped ornotched to provide holding tabs, since a considerably reduced overlap ofthe disc with respect to the end face 17 is required than with a dischaving such holding tabs. Also, in lieu of the conventional retainingshoulder for such prior art scalloped discs, the protuberance 20 fromthe bottom wall of the cavity 19 in the spring retainer serves to limitopening travel of the check valve.

In the modied injector arrangement shown in FIG- URE 3, the springvretainer 14 and spacer block 15 Vare made integral and the springchamber 33 therein has its open end facing the valve body 16'. Thespring seat member 31 is extended in length so that abutment of itsupper end 'against the retainer 14 may limit opening of the needle valve27. The nozzle body and spray 'tip 16 is considerably extended bellowthe nut 3, as is required in certain engines having a relatively smallopening into the combustion chamber for the injector. To minimize thediametral extension of the spray tip the needle valve 27 is providedwith a piston portion 40 and a reduced diameter stem portion 41. Thepiston portion 40'slidably ts the valve body bore 35, and the plungerportion y41 is provided with lateral extensions 42 which laterallysupport and slidably guide it in the bore 35 while accommodating oW offuel longitudinally of the stem portion. These lateral extensions mayconveniently be formed as one or more Hats machined from a land 'sectionintermediate the piston portion and the lower end of the'needle valveand initially of the same cylindrical diameter as the piston portion 40.By this arrangement the drilled passage 25 in the valve body may beangled more obliquely to intersect the injection valve bore 35 at apoint Within the nut 3 Where the Wall thickness of the valve body is ofample dimension for such drilling. As va result, this passage need notextend substantially the whole length -of the extended spray tip Whosediametral extension is `desired to be maintained at a minimum asaforementioned. The Yoperation of the injector is unaffected by thischange in the injection valve and passage arrangement.

While the invention has been described with reference to its preferredstructural embodiment shown in the drawing, it is appreciated that minorchanges may be made therein without departing from the spirit and scopeof the following claims.

What is claimed is:

1. In a unit fuel pump-injector, a pump cylinder open at one end forfuel delivery, an injector opposite said cylinder end having a dischargeoutlet, passage means connecting said cyflinder end and said outlet, avalve movable to close and open said outlet, a spring biasing the valveclosed, said valve having a piston portion connected thereto and exposedto fuel pressure in said passage means for moving said valve in theopening direction against theV biasing force of said spring, a retainerfor said spring, said passage means including a cavity in said retainerfacing and extending laterally of said cylinder open end, and a checkvalve for preventing reverse ovv through said passage means and intosaid cylinder, Ysaid cylinder having a seating surface for said checkvalve when in dlosed position, said retainer having a stop limitingopening movement of the check valve, said stop being located oppositesaid cylinder open end and laterally Vinvvard thereof from said cavity.

2. The invention of claim 1, ywherein said injector ncludes a valve bodyhaving a bore slidably receiving said valve piston portion, said valvehaving a stem portion of smaller cross-section lthan said piston portionextending 'longitudinally within said bore toward said outlet, said stemportion and said bore defining therebetween a portion of said passagemeans.

3. In a unit fuel pump-injector, a pump cylinder open at one end forfuel delivery, an injector opposite the open end of the pump cylinderincluding a valve body, a valve in said body, a valve closing spring anda 4spring retainer interposed between the valve body and said end of thepump cylinder, said rvalve body having a fuel discharge outlet normallyolosed by the valve, said valve being openable against the spring bypump fuel pressure, passage means connecting said discharge outlet Withthe open end of the pump cylinder including a cavity in the springretainer facing said cylinder open end, and a check valve for closingsaid passage means against reverse ow to the pump cylinder, said pumpcylinder having an end face defining its open end and a closure seat forthe check valve, said spring retainer cavity extending 'transversely ofthe pump cylinder for communication with the pump cylinder when thecheck valve is displaced from its seat, and a protuberance on the springretainer 'adjacent said cavity engageable by the check valve to limitits displacement from said seat.

4. The invention of claim 3, wherein said valve body includes acylindrical bore leading to said outlet and said valve includes a pistonportion slidably received in said bore and a stern portion of reduceddiameter extending from said piston portion toward said outlet, saidstem portion having means extending laterally therefrom inter- -rnediateits ends to slidably engage said bore and support said stem portiontherein while accommodating fuel ow longitudinally of said stem, saidpassage means including passages in said body and spring retainerconnecting said 4bore and said cavity.

5. In a unit fuel pump-injector having a pump cylinder open at one endfor fuel delivery, said cylinder having an end face dening its said openend, la check valve closable against said face, and an injector oppositesaid cylinder end including an injection valve openable in response to apredetermined fuel delivery pressure developed by the pump andsupporting means for said check valve and injection valve, said meanshaving a passage Yfor fuel flow to the injection valve from saidcylinder Aopen end including a cavity surrounding the check valve, and aprotuberance in said cavity limiting opening moverment of the checkvalve.

References Cited inthe tile of this patent UNITED STATES PATENTS2,378,165 Waeber June 12, 1945 2,793,076 Brehmer May 21, 1957 2,898,051Teiche'rt v Aug. 4, 1959 2,912,168 LOrange Nov. 10, 1959 2,951,643 EngelSept. 6, 1960 FOREIGN PATENTS 541,100 Great Britain Nov. 12, 1941

